David Beckham sat on the top table at Parc des Princes and followed the script perfectly. Aside from the eye-catching and undeniably noble gesture that he is to donate his hefty salary to a local children's charity, the former England captain spoke glowingly of the Qatari-backed "project" which he will now effectively front. He said he would have to work his way into Carlo Ancelotti's expensively assembled team, massaged the considerable ego of his new club-mate Zlatan Ibrahimovic and even threw in a desire to score against Marseille – just to sweeten any local doubters. At his side the club president, Nasser Al-Khelaifi, basked in his coup.

Paris Saint-Germain will consider this signing to be better late than never. Twice in the past Qatari Sports Investments, owners since the summer of 2011 of French football's greatest under-achievers of modern times, had attempted to lure Beckham from Los Angeles and twice the timing had not been right. A year ago they had believed he was theirs, only for the lure of one last hurrah in Major League Soccer, culminating in a title triumph in December, to scupper their hopes. "I still felt I had something to achieve in Los Angeles last year," said the midfielder. "So we 'parked' it and I accepted one more year in LA. I won another trophy there and that made it the right time to leave.

"I'm very lucky. I'm 37 and had a lot of offers, more now than I've ever had in my career, and at my age, too … I chose Paris because I can see what the club is trying to do. I can see the players the club is bringing in.

"It's an exciting city – it always has been – but now there's a club that will have a lot of success over the next 10, 15 and 20 years. To be a part of something that's growing is very exciting for me. I'm very honoured to have been picked to be a part of the future of PSG – to help this club grow, to help the French league grow and to help this club become one of the biggest powerhouses in football."

There had been 12 offers from around the globe – from South America to Australia, China to Russia – but the sense of ambition, the reality of Champions League football and the unique idea to back a local charity, had apparently swayed him to France. Throw in the chance to work again with Ancelotti, under whom he had played at Milan, and the package appeared even more attractive.

What doubts there are perhaps centre on the Qataris' motivation. The sceptics might argue that, while the Englishman and his entourage had arrived three-quarters of an hour late, the midfielder is actually almost a decade past his best. PSG were supposed to be beyond all the marketing ploys and publicity stunts, as their pursuit of Ibrahimovic, Thiago Silva and Lucas Moura – modern-day galácticos, not fading superstars – had demonstrated. They are reinventing this club as a global contender, as Beckham suggested, but the time to bring in a world famous veteran to push the brand was surely at the start of the project rather than when it was already well under way. Momo Sissoko, the former Liverpool midfielder, may be en route to Fiorentina on loan to free up some space for PSG's new No32 but is the new arrival really likely to play regularly from the start over his five months in France? Surely a bit-part role awaits.

As if to reinforce the point the last question at his unveiling suggested he would become "the grandpa" of Ligue 1, withonly PSG's fourth-choice goalkeeper, Ronan le Crom, older than the midfielder. "It feels very good," offered Beckham through a smile. "To be in Paris, to be at a club like this, to be the elder statesman … I'm very proud of all that. No matter what my age is, I still feel 21 years old. Most days, at least. My fitness won't take long to get up to speed and I've been training with Arsenal. I'll get up to speed."

He will need to, with PSG leading the division only on goal difference from Olympique Lyonnais as they seek a first title since 1994 and with Valencia hardly pushovers in the last 16 of the Champions League to come. The reality, of course, is that Beckham is still Beckham. He will continue to draw the focus, this time to Paris and a club whose image was not helped last week by France Football's documenting of Qatar's controversial, if successful, bid for the 2022 World Cup finals. The former England captain will still be a PR success and marketing man's dream, perhaps even more so than Ibrahimovic on the world stage, staggering as that may seem, given the Swede's talents. Shirts will fly off the shelves and he appears an ambassador in waiting.

And he will also contribute when offered time on the pitch. The slower pace of French football might suit him, for all that he suggested he believed he could have made a mark at an English top-flight club, even if his enduring allegiance to Manchester United prevented him considering that an option. He will be committed and may yet make his mark at set pieces, if he can wrench the ball from Ibrahimovic & Co.

"He will be an asset for the club as a player," stressed Al-Khelaifi. "He is very professional on and off the pitch and I'm sure he will add big value to the club. This is a big day. We've been trying to get him here for a long time and, finally, we have done it. Thank you, David, for believing in our project and being part of our dream."